Process and catalyst for manufacturing cyclic ketones by catalytic dehydrogenation of cyclic alcohols

ABSTRACT

CYCLIC KETONES WITH HIGH SPECIFICITY AND INCREASED YIELDS ARE PRODUCED BY THE CATALYTIC DEHYDROGENATION OF CYCLIC ALCOHOLS. THE CATALYST UTILIZED FOR THE DEHYDROGENATION PROCESS COMPRISES SILICA, ZINC OXIDE, AT LEAST ONE OXIDE OF AN ALKALINE EARTH METAL AND AT LEAST ONE BASIC COMPOUND OF AN ALKALINE METAL.

United States Patent PROCESS AND CATALYST FOR MANUFACTURING CYCLIC KETONES BY CATALYTIC DEHYDRO- GENATION OF CYCLIC ALCOHOLS Bernard Juguin, Rueil-Malmaison, France, assignor to Institut Francais dn Petrole, des Carburants et Lubrifiants, Rueil-Malmaison, France No Drawing. Filed Nov. 15, 1967, Ser. No. 683,120 Claims priority, application France, Nov. 28, 1966,

85,302 Int. Cl. B01j 11/32 U.S. Cl. 252-457 15 Claims ABSTRACT OF THE DISCLOSURE Cyclic ketones with high specificity and increased yields are produced by the catalytic dehydrogenation of cyclic alcohols. The catalyst utilized for the dehydrogenation process comprises silica, zinc oxide, at least one oxide of an alkaline earth metal and at least one basic compound of an alkaline metal.

This invention relates to an improved process for manufacturing cyclic ketones such as cyclohexanone by catalytic dehydrogenation of corresponding alcohols, for example cyclohexanol (which may be manufactured by oxidation of cyclohexane or by any other process). More particularly this invention relates to a process where the catalyst is manufactured by depositing zinc oxide, an alkaline-earth metal oxide and an alkaline compound over an inert carrier consisting of balls, granules or other agglomerates of silica, the chemical ocmposition and the textural characteristics are well determined.

It is known that cyclohexanone is a very important basic, compound for the manufacture of polyamides and that the skilled people are looking for an improvement in the economics of its manufacture.

It is known to carry out such a dehydrogenation by passing cyclohexanol over a catalyst containing zinc oxide, or a mixture of zinc oxide and zinc carbonate with alkaline or alkaline-earth metal compounds, such as calcium or magnesium oxides or carbonates; the reaction temperature is usually between 325 and 475 C. and the pressure between 0.1 and 10 kg./cm.

The reaction is optionally carried out with added hydrogen which is preferably used in an amount of 0.5 to 5 moles per mole of cyclohexanol.

It does not appear that the following results have been obtained simultaneously up to now:

A high conversion rate allowing the use of high rates of reactants.

A selective conversion thereby avoiding the formation of dehydration products, condensation products and, above all, phenol; it is known that phenol is quite detrimental in the further manufacture of caprolactam obtained from cyclohexanone.

A high duration of life allowing the use of the catalyst on the industrial scale.

A great ease of regeneration of the catalyst by combustion of carbon deposits.

A satisfactory solution has been brought to these problems by the present invention.

This new process is based on the use of a catalyst containing silica, zinc oxide, at least one oxide of an alkalineearth metal and at least one compound of an alkaline metal which imparts to the catalyst a basic reaction.

Preferably the catalyst is obtained by depositing the active elements (zinc oxide and oxide of alkaline-earth metal) or their precursors (convertible into these active 3,560,406 Patented Feb. 2, 1971 elements) on a carrier consisting of a preferably activated silica (Le. previously heated up to a temperature between about 300 and 800 C.) containing about 0.2 to 5%, preferaby 0.4 to 2% by weight of a basic compound of an alkaline metal, the weight being expressed as M 0 where M is the alkaline metal.

There will be advantageously chosen a silica having a specific surface higher than 15 rnP/g. and for example between 15 and 300 m. /g. (preferably 25-150 m. /g.). Preferably the carrier will have a total porous volume of 0.8-1.3 cm. /g., usually at least 80% of this porous volume corresponding to pores with an average diameter between 100 and 500 angstroms.

The ZnO content of the obtained catalyst will be most advantageously between 8 and 25% by weight (preferably 15-20%), whereas the content of alkaline-earth metal oxide will be advantageously between 15 and of the weight of ZnO (more preferably 25-40%). These figures are optimal values; satisfactory results may also be obtained with amounts of 2-50% by weight of ZnO and 05-30% by weight of alkaline-earth metal oxide, with respect to the total weight of catalyst.

As a rule the catalyst will contain 0.2-5% by weight of the basic compound of the alkaline metal, expressed as M 0, preferably 0.4-2%. It is however preferred that this compound be present in the carrier, before manufacturing the catalyst.

If the carrier contains less than 0.4% and, of course, less than 0.2% of these metals, the parasitic reaction of dehydration of cyclohexanol is improved, whereas beyond 2%, and of course beyond 5%, the condensation reactions of the cyclohexanone are troublesome.

It is essential that the alkaline metal be in the form of a free base. The presence of stable salts of alkaline metals,

' particularly the sulfate and the chloride, is detrimental and increases the intensity of the parasitic reaction of dehydration.

ZnO and the alkaline-earth metal oxide (preferably calcium oxide) will be preferably deposited on the silica by means of solutions containing the oxides, or solutions of zinc and alkaline-earth metal inorganic or organic compounds, these compounds being able to decompose under the manufacture or use conditions of the catalyst, thus forming the corresponding oxides. There will be named by way of non-limitative examples the solutions of zinc nitrate, acetate, tartrate, lactate, citrate, laurate and oleate, and the solutions of alkaline-earth metal nitrate,

' oleate, laurate, acetic, tartrate, lactate or citrate, particularly those of magnesium, calcium, barium and strontium.

These solutions are usually acid; in order to retain a good selectivity, it is preferable to neutralize this acidity by further addition to the catalyst of compounds having a basic reaction or able to decompose under the manufacture or use conditions of the catalyst to liberate basic compounds.

As examples of basic compounds of alkaline metals which may be present in the silica or introduced as neutralizing agents, the alkaline metal oxides and hydroxides will be named, as well as the carbonates and other salts of weak acids with these metals, for example potassium oxide, sodium hydroxide, potassium hydroxide, lithium hydroxide, sodium carbonate, potassium bicarbonate, rubidium carbonate and cesium carbonate.

The amount by weight (expressed as alkaline metal hydroxide) of the additional alkaline metal compound added at this stage of the process will be advantageously between 0.05 and 0.2 times the amount by weight of ZnO, preferably between 0.1 and 0.15 times this amount, the essential rule being to neutralize the acidity brought by the impregnating solutions, a small excess of base not modifying appreciably the properties of the catalyst.

The order of the impregnation operations is of appreciable importance and it is preferred to bring zinc oxide and the alkaline-earth metal oxide before the neutralizing element. The catalysts which are manufactured in the reverse order exhibit lower performances with respect to selectivity.

The impregnated catalyst is finally dried and roasted for example above 300 C.

The best catalysts have been obtained by use of the following operations in the order:

(1) Impregnation of the carrier (silica preferably containing 0.42% by Weight of alkaline metal, expressed as M by means of an aqueous solution containing the zinc compound and the alkaline-earth metal compound. However distinct solutions may be used for each metal.

(2) Drying, at least partial, for example at about 60 (3) Impregnation by means of an aqueous solution of the alkaline compound which is used to counterbalance the acidity of the previous solutions.

(4) Drying, for example at about 100110 C.

(5) Calcination by heating, for example for 2-7 hours, preferably under air current, at a temperature of 350- 700 C.

The operations No. 3 and 4 may be omitted if the impregnating solutions of the No. 1 are not acid.

The conditions of use of these catalysts are also of importance. In order to obtain high conversion rates and selectivities, the temperature will be chosen between 350 and 450 C., preferably between 370 and 420 C., for hourly feed rates of liquid cyclohexanol amounting to about 0.5 to 8 times the volume of catalyst, advantageously 1.5 to 5, with absolute pressures of 0.1-10 kg./cm. preferably 12 kg./cm. Hydrogen is preferably used at a rate of 0.2-5 moles per mole of alcohol.

The following non-limitative examples illustrate this invention:

EXAMPLE 1 A catalyst is prepared containing approximately 18% by weight of zinc oxide, 6% by weight of calcium oxide, 2% by weight of potash deposited on a silica containing 1% by Weight of Na O.

There is used 200 cm. of extrudates of silica with a density of 0.37, i.e. 74 g., their specific surface being The impregnated extrudates are then dried for 12 hours in an oven at 90 C. 75 cm. of a solution containing 2 g. KOH are then used for impregnation in order to counter-balance the acidity brought by the solution of nitrates. The contact is maintained for 10 hours and the extrudates are then dried at 100-110 C. for 12 hours. The catalyst is then roasted for 5 hours at 450 C. in an air current.

After calcination the specific surface of the catalyst is 22 m. g.

The catalyst then constitutes the catalyst C of Table I. It has the following composition:

Percent ZnO 17.6 CaO 5.8 K 0 1.4 N320 0-7 SiO 74.5

These values have been determined by chemical analysis.

EXAMPLE 2 This example shows the influence, on the selectivity, of the inertness of the catalytic carrier.

Operating as in Example 1, three catalysts A, B and C are manufactured with 18% ZnO, 6% calcium oxide and 2% KOH deposited on silica extrudates with the same textural characteristics (specific surface of 35 m. /g., porous volume of 115 cm. per 100 g.); however the Na O amounts by weight differ:

Catalyst A: 0.15% Na O with respect to carrier Catalyst B: 0.5% Na O with respect to carrier Catalyst C: 1% Na O with respect to carrier Pure cyclohexanol, obtained by hydrogenation of phenol, is passed over these three catalysts under the following conditions:

Temperature: 400 C.

Absolute pressure: 1.5 kg./cm.

Feed rate: 4 liters of liquid cyclohexanol per liter of catalyst per hour.

Molar ratio hydrogen/cyclohexanol at the inlet of the reaction vessel: 1.

The results are given in Table I, from which is can be seen that it is important to have a neutral carrier at the beginning of the catalyst manufacture.

TABLE I Composition of the product (by weight) Cyclo- Cyclo- Hydrohexanol, hexanone, carbons, Water, Conversion, Selectivity, percent percent percent percent percent percent Catalyst:

A 24 65.5 8 2 76 86.3 B- 25.4 73.1 1.2 0.3 74.6 98 C 26 73. 9 0. 1 0 74 99. 8

35 m. /g., the total porous volume 115 cm. per 100 g. EXAMPLE 3 and the amount of Na O being 1% by Weight.

The following solution is prepared:

Zinc nitrate: Zn(NO 6H O65.8 g. Calcium nitrate: Ca(NO 17.6 g. Distilled water cm.

Percent KOH by weight Catalyst D 0:5 Catalyst E 1 Catalyst F (identical to catalyst C) 2 Catalyst G 5 Pure cyclohexanol is passed over these 4 catalysts under the operating conditions of Example 2.

The results are given in Table II.

It may be observed that the amount of alkaline metal compound with which the carrier is impregnated has some influence on the selectivity of the catalyst; how- 6 EXAMPLE 5 This example shows the influence of the method of manufacture and particularly that the order of the impregnation operations has a big influence.

Pure cyclohexanol and hydrogen are passed over a catalyst containing 18% of ZnO, 6% of CaO and 2% of KOH deposited on silica extrudates having the following textural characteristics:

Specific surface-35 m. /g. Total pore volume1l5 T cm. 100 g. Na O content by weight-1% The catalyst is manufactured as in example 1, i.e. ZnO and CaO are deposited before KOH.

ever influence is lowfir than of the inertness 15 The operating conditions are those of Example 2 0f the C The raw product issuing from the reaction zone has The optimal amount of alkaline metal compound the f ll wi composition by Weight; is about 10-15 of the amount of ZnO; beyond P t the selectivity does not increase appreciably, however ercen the catalytic activity decreases. Cyclohexanol Cyclohexanone 73.9 EXAMPLE 4 Hydrocarbons 0.1

This eXamp1e shows 'f influence 9 the textllfal which represents a conversion rate of 74% and a seleccharacteristics of the carrier over the actlvlty, selectrvlty tivity towards Cyclohexanone f 99 g% (See Catalyst C and stability of the catalyst. of Example 2),

Three Catalysts 3R manufactured, H, I and I, each After 20 hours in the same operating conditions, the COIItaiHiHg 13% Z110, CH0 and 2% KOH, product had the following composition by weight: posited on silica extrudates, using the process of Examp16 Percent The specific surfaces of the 3 carriers are different: Cyclohexanol 2/ Cyclohexanone 73.4 Hydrocarbons 0.1 Catalyst H 8 Catalyst I which represents a conversion rate of 73.5% and a selec- Catalyst 1 140 tivity toward cyclohexanone of 99.9%.

By Way of comparison, the same reactants are passed The amounts by Welght of Nazo these three under identical conditions over a catalyst containing 18% nets are i Same: ZnO, 6% CaO and 2%KOH, deposited on the same fl lmpregnatlon and calclnatlon the respeqtlve carrier. The process for manufacturing the catalyst is specific surfaces of these 3 catalysts were the following: different, Since KOH is deposited bgfore ZHO and C210 M The resulting product had the following composition Catalyst H 1 y welghti Catalyst I (as catalyst C) 22 Percent Catalyst] 83 Cyclohexanol 27 Cyclohexanone 71.4

These three catalysts have been Used Wl h pure Y Hydrocarbons 1.3 hexanol. Water 0,3

The operating conditions and results are given in Table III (the pressure, in all cases is 1.5 atmospheres and the which corresponds to a conversion rate of 73% and a molar ratio H /cyclohexanol is 1): selectivity toward cyclohexanone of 97.8 %only.

TABLE III Operating conditions Tempera- Working Percent Percent tu1'e, C. V.v.h. time conversion selectivity Catalyst: 1 67 9 8 H 1 2( 66. 2 I 4 i 20 73. 3 3 12 J 4 i 20 7s. 3 99. 8

N0Tn.-V.v.l1.:vo1ume of liquid cyclohexanol per volume of catalyst and per hour.

It may be observed that:

(a) the selectivities and stabilities of the 3 catalysts are good.

(b) the activity, i.e. the conversion rate, increases with the specific surface of the catalyst.

Industrially the catalyst having a large specific surface will be preferred since it allows the use of higher feed velocities, or working at lower temperatures.

After 10 hours under the same operating conditions, the resulting product had the following composition:

which corresponds to a conversion rate of 68% and a selectivity of 95.5%.

7 Thus, in order to obtain a very selective and stable catalyst it is necessary to follow the operating steps of Example 1.

EXAMPLE 6 ZnO, CaO, KOH, percent percent percent Catalyst K 9 3 1 L 18 6 2 M- 24 8 2. 7

After impregnation and roasting, the specific surfaces of these 3 catalysts were the following:

MF/g. Catalyst K 29 Catalyst L (as catalyst C) 22 Catalyst M 14 Pure cyclohexanol has been passed over these 3 catalysts under the operating conditions of Example 2.

The results are given in Table IV.

TABLE IV Times Percent Percent (hours) conversion selectivity Catalysts:

K 1 71 00. 7 20 (as on. s L l 7-l 99. 8 20 73. 5 or). 9 1 68 00. 0 M 20 67. c as. 0

It may be concluded:

that the selectivity of the 3 catalysts is quite good that the initial activity of catalyst K is pretty good; however its stability is bad. This good initial activity could be probably ascribed to the rather large specific surface of the catalyst that the stability of catalysts L and M is quite good that the initial activity of catalyst M is lower; the lower specific surface of this catalyst is probably responsible of this lower activity.

Thus an optimal amount of ZnO is preferably used;

this is between and EXAMPLE 7 Following the general process of Example 1, however using zinc acetate and calcium acetate instead of the corresponding nitrates, catalysts are obtained which exhibit a somewhat increased activity.

These catalysts have been used for 3,600 hours without noticeable deactivation.

EXAMPLE 8 The steps of Example 1 are followed, except that zinc and calcium citrates are used instead of the corresponding nitrates. The catalyst is somewhat more active and selective than the reference catalyst.

EXAMPLES 9', 10 AND 11 Example 1 is repeated except that barium, strontium and magnesium carbonates respectively are substituted for calcium nitrate, so that the weights of corresponding oxides, after impregnation and calcination, amount to 6% of the weight of the catalyst.

The resulting catalysts are somewhat more active than the reference catalyst.

8 EXAMPLES 12 13 Example 1 is repeated except that zinc and calcium tartrates, on the one part, zinc and calcium lactates, on the other part, are substituted for the corresponding nitrates. The resulting catalysts are slightly more selective than the reference catalyst.

EXAMPLE 14 Two catalysts N and O are prepared, which are identical to catalyst C, except that the amounts of CaO are respectively 3% and 9%.

Under the experimental conditions of Example 2, the following results have been obtained:

Percent Time Percent Percent CaO (hours) conversion selectivity Catalyst 1 g 5 77 s. N 3 l 20 73 98.9 1 70 99.9 0 9 2( 70.2 9 7 .8 O 6 i 20 73. 5 99. 9

I claim: 1. A catalyst containing silica, zinc oxide, an alkalineearth metal oxide and an alkaline metal compound prepared by admixing silica containing 0.2-5% by weight of an alkaline metal compound selected from the group consisting of oxides, hydroxides and carbonates, expressed as M 0 where M is the alkaline metal, with aqueous solutions of a zinc compound and an alkaline earth metal compound, said alkaline earth metal compound being selected from the group consisting of nitrates, acetates, citrates, lactates, tartrates, laurates and oleates, the weight of the zinc compound, expressed as ZnO, amounting to 250% with respect to the catalyst, the weight of the alkaline-earth metal compound, expressed as oxide amounting to 0.530% with respect to the catalyst, drying the resulting mixture and roasting the latter at 350- 700 C.

2. A catalyst as claimed in claim 1, the weight of said alkaline metal compound being about 10/ 15% of the amount of said zinc oxide compound.

'3. A catalyst as claimed in claim 1, wherein the weight of the zinc compound, expressed as ZnO, is between 8- 25% with respect to said catalyst, the weight of the alkaline-earth metal compound, expressed as oxide is between 15-50% with respect to said zinc oxide the weight of said alkaline metal compound is 0.4 to 2% with respect to said catalyst.

4. A catalyst as claimed in claim 1, wherein the silica exhibits a specific surface higher than 15 m. /g.

5. A catalyst as claimed in claim 1, wherein the silica exhibits a porous volume of 0.8-1.3 cm. /g. and a specific surface of 15-300 m. /g.

6. A catalyst as claimed in claim 1, wherein the amount of zinc oxide is 15-20% by weight.

7. A catalyst as claimed in claim 1, consisting of zinc oxide, calcium oxide and potassium hydroxide incorporated into a silica containing sodium oxide.

8. A catalyst according to claim 1, wherein the silica is an activated silica exhibiting a specific surface of l5 300 mF/g. and an amount of alkaline metal compound between 0.4 and 2% by weight, measured as M 0.

9. A catalyst according to claim 1, wherein the silica containing said alkaline metal compound is first impregnated with an aqueous solution containing the zinc compound and the alkaline-earth metal compound, then dried, impregnated with an aqueous solution of a second alkaline metal compound selected from the group consisting of carbonates, hydroxides, and oxides, said second alkaline metal compound being the same as or different than said alkaline metal compound and then dried and roasted.

10. A catalyst according to claim 1, wherein the zinc and alkaline earth metal compounds are impregnated as aqueous solutions of nitrates, acetates, citrates, lactates, tartrates, laurate or oleates.

11. A catalyst according to claim 1, wherein said alkaline metal compound is sodium oxide, potassium oxide, sodium hydroxide, potassium hydroxide, lithium hydroxide, sodium carbonate, potassium bicarbonate, rubidium carbonate or cesium carbonate, and said alkaline earth metal compound is a compound of magnesium, calcium, barium or strontium.

12. A catalyst according to claim 1, wherein said alkaline metal compound is sodium oxide, said zinc compound is zinc nitrate, and said alkaline earth metal compound is calicum nitrate.

13. A catalyst according to claim 9, wherein said alkaline metal compound is sodium oxide, potassium oxide, sodium hydroxide, potassium hydroxide, lithium hydroxide, sodium carbonate, potassium bicarbonate, rubidium carbonate or cesium carbonate, and said alkaline earth metal compound is a compound of magnesium, calcium, barium or strontium.

14. A catalyst according to claim 9, wherein said alkaline metal compound is sodium oxide, said zinc com- 10 pound is zinc nitrate, said alkaline earth metal compound is calcium nitrate, and said second alkaline metal compound is potassium hydroxide.

15. A catalyst according to claim 9, wherein said second alkaline metal compound is potassium hydroxide.

References Cited UNITED STATES PATENTS DANIEL E. WYMAN, Primary Examiner C. F. DEES, Assistant Examiner US Cl. X.R. 2605 86 

